WO 9635906 A1 describes a coupling for hydraulic ducts with a female coupling and a male coupling. The female coupling has a receptacle which receives the male coupling through an opening of the receptacle. The opening includes an inner circumferential groove which receives a multitude of locking elements. The locking elements, in form of annular segments supporting one another, are distributedly arranged around the circumference of the inner circumferential groove. The locking elements are springingly acted upon by an elastic O-ring towards the inside at the end of the inner circumferential groove distanced from the opening. The locking elements, together in a locking position, form a conical inner circumferential face and project partially from the inner circumferential groove to the inside.
The male coupling has a displacement face at its end insertable into the female coupling. The displacement face interacts with the inner faces of the locking elements such that the locking elements are moved from the locking position outwardly into the releasing position. In this position, the locking elements are completely arranged within the inner circumferential groove to receive the male coupling. The male coupling, further, has an outer circumferential groove. The locking elements are pressed into the outer groove by the elastic O-ring, as soon as the male coupling is inserted far enough into the receptacle. In this position of the male coupling, the locking elements are axially supported on the support face of the inner circumferential groove as well as on a locking face of the outer circumferential groove. Thus, the male coupling is retained against withdrawal.
A plastic ring is provided within the outer circumferential groove of the male coupling. The plastic ring is narrower than the outer circumferential groove. If the male coupling is inserted further into the receptacle, the locking elements slide on the outer circumferential face of the plastic ring. Thus, the locking elements are moved into the releasing position. The friction force between the locking elements and the plastic ring is higher than the friction force between the plastic ring and the male coupling. Thus when withdrawing the male coupling connector, the plastic ring slides within the outer circumferential groove till it abuts the locking face of the outer circumferential groove. The outer diameter of the plastic ring is at least as large as the outer diameter of the male coupling at its end. Accordingly, when further pulling out the male coupling, the locking elements slide from the plastic ring onto the outer circumferential face of the male coupling and the male coupling can be completely pulled out of the female coupling.
A disadvantage in this coupling is that when a locking element is loosened, the residual locking elements are not held in the inner circumferential groove since they cannot support each other. Furthermore, a high number of components is necessary making the assembly cumbersome. Furthermore, the plastic ring is loaded by a high mechanical loading. Thus, the outer diameter of the plastic ring may be reduced or worn off so that the ring becomes smaller than the outer diameter of the male coupling. This causes a jamming of the male coupling during withdrawal.
DE 199 32 307 A1 discloses a coupling with a female coupling having a receptacle. A male coupling is inserted through an opening of the receptacle. A circlip sits in an inner circumferential face of the receptacle. The circlip projects with a portion of its cross-sectional face radially to the inside. The male coupling has a displacement face on its end. The displacement face pushes the circlip radially deeper into the inner circumferential groove during the insertion of the male coupling into the receptacle. Thus, the male coupling can be received in the female coupling. The male coupling has an outer circumferential groove, into which the circlip, after further insertion of the male coupling, enters. In this position, the circlip is axially supported on the locking face of the outer circumferential groove as well as on the locking face of the inner circumferential groove. Thus, the male coupling is retained against withdrawal.
An annular gap is formed between the female coupling and the male coupling starting from the opening of the receptacle. An unlocking sleeve is inserted into the gap from the outside into the receptacle. Due to axial displacement of the unlocking sleeve into the receptacle, the circlip is axially moved along the conical locking face of the outer circumferential groove. This widens and radially pushes the circlip out of the outer circumferential groove so that the male coupling can again be removed from the receptacle.
The locking face of the outer circumferential groove is formed as steep as possible towards the longitudinal axis. Thus, the angle which the conical locking face encloses is as large as possible. This ensures the best possible axial support of the circlip between the locking face of the outer circumferential groove and the locking face of the inner circumferential groove. Accordingly, a high force has to be applied to push the circlip out of the outer circumferential groove. Furthermore, there is a danger that the circlip may widened irregularly and thus not widened round because it is cut at one position. Thus, the ends of the circlip can lock between the locking faces.
DE 26 27 397 A1 describes a coupling having a male coupling and a female coupling. A holding element has a ring, which forms a collar extending radially inside towards the longitudinal axis. Radially extending spring elements are formed on the ring. The spring elements are radially elastically formed. The collar of the ring rests in a circumferential groove of the male coupling. This fixes the holding element on the male coupling. The ring is cut at one position, to enable an assembly.
A groove is provided at the free ends of the spring elements. A collar extending radially towards the longitudinal axis engages the grooves when the male coupling is inserted into the female coupling. Therefore, the male coupling is securely held in the female coupling. Thus, during loading in a withdrawal direction, the spring elements are tensioned and retain the male coupling. An unlocking sleeve is arranged around the holding element. The unlocking sleeve slides during the displacement towards the female coupling in the insertion direction of the male coupling into the female coupling. The unlocking sleeve pushes against abutment faces of the spring elements pushing them radially to the inside until the collar of the female coupling does not rest in the groove of the spring elements. This enables withdrawal of the male coupling.
A disadvantageous is that the spring elements in the connected condition of the coupling, are tensioned and are correspondingly massively formed. Because of this, a large annular gap is necessary between the male coupling and the female coupling to enable passage of the spring elements. Furthermore, when releasing the coupling, the unlocking sleeve has to be moved against the withdrawal direction of the male coupling, so that a single-handed operation is not possible.